合成氨油改气低温甲醇洗单元低温平衡技术方案的选择

根据合成氨装置的特点，针对油改气后原料变化对低温甲醇洗单元的影响，提出相应的技术方案。经过分析比较，最终选择减少溶液循环量、向系统补冷与CO2循环相结合的技术方案，以保证低温甲醇洗单元维持低温平衡操作，消除由于原料气中CO2含量降低对低温甲醇洗及下游装置造成的影响。改造后，整个装置运行稳定，低温甲醇洗单元的各项性能指标均达到了设计要求，半贫甲醇操作温度-77℃，较改造前降低6℃；净化气中CO2体积分数≤20×10^-6；产品气中CO2体积分数≥97．5％。

Selection of Technological Plans for Equilibrium at Low Temperature in Low-Temperature Methanol Wash Unit after Change of Ammonia Feedstock from Oil to Gas

In line with the characteristics of the ammonia plant, an appropriate technological plan is proposed to cope with the effect on the low-temperature methanol wash unit after the change of feedstock from oil to gas. Through analysis and comparison a technological plan is finally chosen that combines a decrease in solution recycle, replenishment of cold to the system, and recycle of CO2, so as to ensure that the low-temperature methanol wash unit maintains its operation at low-temperature equilibrium, thereby eliminating the effect on the low-temperature methanol wash and its downstream units caused by the decrease in the CO2 content of the feed gas. After revamp, the whole plant runs steadily, the various performance indices of the low-temperature methanol wash unit reach the design requirements, and the operating temperature of the semi-lean methanol is - 77 ℃, 6 ℃ lower than that before revamp ; the CO2 volume fraction in the purified gas is ≤20×10^-6 ; and the CO2 volume fraction in the product gas is ≥97.5%.